Conventional light emitting diode (LED) materials, such as GaAs, have allowed the construction of only single junction or multiple parallel junction devices when fabricated monolithically. FIG. 1A illustrates a typical multiple parallel junction LED array 10. Several p-type regions 13 are grown over a common n-type region 18. N-contact 11 connects to n-type region 18 and several p-contacts 14 connect to p-type regions 13. The device is fabricating by forming n-type region 18 on a substrate 12, then forming a continuous p-type layer over the n-type region. The p-type layer is then divided into discrete regions by mechanically sawing or chemically etching trenches 15 between p-type regions 13. FIG. 1B illustrates another multiple parallel junction LED array 16. Instead of mechanical sawing or chemical etching, p-type regions 13 are electrically isolated from each other by diffusion. The monolithic arrays illustrated in FIGS. 1A and 1B are limited to the parallel configuration illustrated in FIG. 2 because the use of contacts on opposite sides of the device requires one common conductive layer, i.e., n- or p-layer.
In accordance with the present invention, a series or parallel LED array is formed on an insulating or highly resistive substrate, such that both the p- and n-contacts for the array are on the same side of the array. The individual LEDs are electrically isolated from each other by trenches or by ion implantation. Interconnects deposited on the array connect the contacts of the individual LEDs in the arrays. In some embodiments, the LEDs are III-nitride devices formed on sapphire substrates. In one embodiment, the III-nitride devices are formed on high-resistance SiC or III-nitride substrates. In one embodiment, two LEDs formed on a single substrate are connected in antiparallel to form a monolithic electrostatic discharge protection circuit. In one embodiment, multiple LEDs formed on a single substrate are connected in series. The series array can operate at a higher voltage than a single LED of the same area, thus simplifying power supply design. In one embodiment, multiple LEDs formed on a single substrate are connected in parallel. In this embodiment, multiple p-type regions are formed on a single n-type region, such that the n-type region surrounds each of the p-type regions and interposes the p-type regions. In some embodiments, a layer of phosphor covers a portion of the substrate on which one or more individual LEDs are formed.